Potential mechanisms linking low-fat diet to inflammation and metabolic syndrome

Effect of low-carbohydrate diet on adiponectin level in adults: a systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND

To the best of our knowledge, no previous study has reported findings on the effects of low-carbohydrate diet (LCD) on adiponectin concentration.

OBJECTIVE

The current systematic review and dose-response meta-analysis was carried out to systematically review the available controlled clinical trials about the effect of LCD on adiponectin level in adults.

METHODS

Literature searches of PubMed/Medline, Scopus and Web of Sciences were conducted up to August 2019. Randomized controlled trials (RCTs) which assessed the effect of LCD on the adiponectin level were selected.

RESULTS

Eleven studies, including 1047 participants (LCD = 534 and control = 513), were included in the meta-analysis. Proportion of carbohydrate from calorie was from 4 to 34%. Time of the follow-up varied between studies and ranged from 6 to 152 weeks. LCD intake mildly but significantly increased adiponectin (0.02 µg/ml, 95% CI: 0.01 to 0.03, P < 0.001). Dose-response analysis indicated a nonlinear association between the percentage of carbohydrate and change in adiponectin level from baseline (P = 0.04). After subgroup analysis based on the proportion of carbohydrate from calorie, there was a significant increase in adiponectin concentration in studies that prescribed <30% of calorie from carbohydrates (0.12 µg/ml, 95% CI: 0.07-0.18). In contrast, diets which consisted ≥30% of carbohydrates had no significant effect on adiponectin (0.50 µg/ml, 95% CI: -0.46 to 1.48). Also, meta-regression analysis revealed that age (β = 0.04, P = 0.15), baseline BMI (β= -0.15, P = 0.15), time of follow-up (β = 0.01, P = 0.17), percentage of carbohydrates (β = 0.004, P = 0.90), percentage of protein (β= -0.12, P = 0.08), percentage of fat (β = 0.20, P = 0.61) and baseline adiponectin (β = 0.001, P = 0.97) are not sources of heterogeneity.

CONCLUSION

This systematic review and meta-analysis demonstrated a mild but significant effect of LCD on adiponectin concentration compared to control groups.

Protein-Pacing Caloric-Restriction Enhances Body Composition Similarly in Obese Men and Women during Weight Loss and Sustains Efficacy during Long-Term Weight Maintenance

Short-Term protein-pacing (P; ~6 meals/day, >30% protein/day) and caloric restriction (CR, ~25% energy deficit) improves total (TBF), abdominal (ABF) and visceral (VAT) fat loss, energy expenditure, and biomarkers compared to heart healthy (HH) recommendations (3 meals/day, 15% protein/day) in obese adults. Less is known whether obese men and women respond similarly to P-CR during weight loss (WL) and whether a modified P-CR (mP-CR) is more efficacious than a HH diet during long-term (52 week) weight maintenance (WM). The purposes of this study were to evaluate the efficacy of: (1) P-CR on TBF, ABF, resting metabolic rate (RMR), and biomarkers between obese men and women during WL (weeks 0–12); and (2) mP-CR compared to a HH diet during WM (weeks 13–64). During WL, men (n = 21) and women (n = 19) were assessed for TBF, ABF, VAT, RMR, and biomarkers at weeks 0 (pre) and 12 (post). Men and women had similar reductions (p < 0.01) in weight (10%), TBF (19%), ABF (25%), VAT (33%), glucose (7%–12%), insulin (40%), leptin (>50%) and increase in % lean body mass (9%). RMR (kcals/kg bodyweight) was unchanged and respiratory quotient decreased 9%. Twenty-four subjects (mP-CR, n = 10; HH, n = 14) completed WM. mP-CR regained significantly less body weight (6%), TBF (12%), and ABF (17%) compared to HH (p < 0.05). Our results demonstrate P-CR enhances weight loss, body composition and biomarkers, and maintains these changes for 52-weeks compared to a traditional HH diet.

Consuming a hypocaloric high fat low carbohydrate diet for 12 weeks lowers C-reactive protein, and raises serum adiponectin and high density lipoprotein-cholesterol in obese subjects

OBJECTIVE

High fat, low carbohydrate (HFLC) diets have become popular tools for weight management. We sought to determine the effects of a HFLC diet compared to a low fat high carbohydrate (LFHC) diet on the change in weight loss, cardiovascular risk factors and inflammation in subjects with obesity.

METHODS

Obese subjects (29.0-44.6 kg/m2) recruited from Boston Medical Center were randomized to a hypocaloric LFHC (n=26) or HFLC (n=29) diet for 12 weeks.

RESULTS

The age range of subjects was 21-62 years. As a percentage of daily calories, the HFLC group consumed 33.5% protein, 56.0% fat and 9.6% carbohydrate and the LFHC group consumed 22.0% protein, 25.0% fat and 55.7% carbohydrate. The change in percent body weight, lean and fat mass, blood pressure, flow mediated dilation, hip:waist ratio, hemoglobin A1C, fasting insulin and glucose, and glucose and insulin response to a 2h oral glucose tolerance test did not differ (P>0.05) between diets after 12 weeks. The HFLC group had greater mean decreases in serum triglyceride (P=0.07), and hs-CRP (P=0.03), and greater mean increases in HDL cholesterol (P=0.004), and total adiponectin (P=0.045) relative to the LFHC. Secreted adipose tissue adiponectin or TNF-α did not differ after weight loss for either diet.

CONCLUSIONS

Relative to the LFHC group, the HFLC group had greater improvements in blood lipids and systemic inflammation with similar changes in body weight and composition. This small-scale study suggests that HFLC diets may be more beneficial to cardiovascular health and inflammation in free-living obese adults compared to LFHC diets.